Slide out rooms are a popular solution in the recreational vehicle (RV) industry to add interior space and due to their nature are difficult to seal. A major difficulty in sealing RV slide out rooms arises in the corners. Wiper seals and bulb seals have been used in the past with success to nearly completely seal slide out rooms when retracted and extended. A weakness of present systems is that they often lack ability to seal the corners. This is because traditional extruded seals are cut to length squarely, but the corners are not mitered. This provides a potential for leakage in the corners. Having mitered corners where the seals meet outside of the opening through which the slide out room moves could provide a method for sealing that would prevent water from entering at the corners where seals meet. It is desirable to have a sealing method that provides an outer seal to span an area where square cut seals meet to prevent leakage at corners of the slide out opening.